fs/ext4/bitmap.c

   1 /*
   2  *  linux/fs/ext4/bitmap.c
   3  *
   4  * Copyright (C) 1992, 1993, 1994, 1995
   5  * Remy Card (card@masi.ibp.fr)
   6  * Laboratoire MASI - Institut Blaise Pascal
   7  * Universite Pierre et Marie Curie (Paris VI)
   8  */
   9
  10 #include <linux/buffer_head.h>
  11 #include <linux/jbd2.h>
  12 #include "ext4.h"
  13
  14 #ifdef EXT4FS_DEBUG
  15
  16 static const int nibblemap[] = {4, 3, 3, 2, 3, 2, 2, 1, 3, 2, 2, 1, 2, 1, 1, 0};
  17
  18 unsigned int ext4_count_free(struct buffer_head *map, unsigned int numchars)
  19 {
  20         unsigned int i, sum = 0;
  21
  22         if (!map)
  23                 return 0;
  24         for (i = 0; i < numchars; i++)
  25                 sum += nibblemap[map->b_data[i] & 0xf] +
  26                         nibblemap[(map->b_data[i] >> 4) & 0xf];
  27         return sum;
  28 }
  29
  30 #endif  /*  EXT4FS_DEBUG  */
  31
  32 int ext4_inode_bitmap_csum_verify(struct super_block *sb, ext4_group_t group,
  33                                   struct ext4_group_desc *gdp,
  34                                   struct buffer_head *bh, int sz)
  35 {
  36         __u32 hi;
  37         __u32 provided, calculated;
  38         struct ext4_sb_info *sbi = EXT4_SB(sb);
  39
  40         if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
  41                                         EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
  42                 return 1;
  43
  44         provided = le16_to_cpu(gdp->bg_inode_bitmap_csum_lo);
  45         calculated = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)bh->b_data, sz);
  46         if (sbi->s_desc_size >= EXT4_BG_INODE_BITMAP_CSUM_HI_END) {
  47                 hi = le16_to_cpu(gdp->bg_inode_bitmap_csum_hi);
  48                 provided |= (hi << 16);
  49         } else
  50                 calculated &= 0xFFFF;
  51
  52         return provided == calculated;
  53 }
  54
  55 void ext4_inode_bitmap_csum_set(struct super_block *sb, ext4_group_t group,
  56                                 struct ext4_group_desc *gdp,
  57                                 struct buffer_head *bh, int sz)
  58 {
  59         __u32 csum;
  60         struct ext4_sb_info *sbi = EXT4_SB(sb);
  61
  62         if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
  63                                         EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
  64                 return;
  65
  66         csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)bh->b_data, sz);
  67         gdp->bg_inode_bitmap_csum_lo = cpu_to_le16(csum & 0xFFFF);
  68         if (sbi->s_desc_size >= EXT4_BG_INODE_BITMAP_CSUM_HI_END)
  69                 gdp->bg_inode_bitmap_csum_hi = cpu_to_le16(csum >> 16);
  70 }